Conventional electrically powered wheelchairs are typically powered by motors connected to a separate gearbox. The typical gearbox is a right-angled gearbox. Stopping the wheelchair is accomplished by a brake, which is typically connected externally to the motor.
Since the wheelchair must be able to turn in a very tight radius, conventionally powered wheelchairs typically have two drive wheels, which can be rotated independently of one another. Each drive wheel is driven by a gearbox, which in turn is driven by a motor. A brake is typically connected to the outside of the motor. To supply power to the motors, the wheelchair is typically outfitted with one or more batteries. The batteries are typically rechargeable, so that the operator can easily recharge the batteries by simply plugging into a wall electrical outlet.
The use of two motors, two gearboxes, an external brake, and the batteries to supply power results in a great demand for space to accommodate all of these components. Typically, a portion of the frame of a conventional wheelchair is reserved for mounting of the batteries and the drive mechanism. The motor, gearbox, and external brake take up a lot of space on a convention wheelchair, leaving little space for installing batteries and other equipment. The gearboxes and motors add to the weight of the wheelchair, increasing the power drain and decreasing the charge of the batteries as the wheelchair is operated.
FIGS. 1 and 2 depict a portion of a prior art wheelchair 20 including a frame 22, drive wheels 24, batteries 26, and a drive mechanism 28. The drive mechanism 28 is a right angle gearmotor 30 comprised of a motor 32 and a gearbox 34. In powered vehicles for handicapped persons, such as wheelchairs and scooters, the vehicle must include a safety feature that stops the vehicle whenever the vehicle controller is set to the neutral position. Typically, the controller includes a joystick (not shown) that is manipulated by the wheelchair user to control the vehicle. In the conventional wheelchair, a brake 36 mounted external to the motor 32 acts as a safety brake, stopping the rotation of the drive wheels 24 at the appropriate times as the controller is placed in the neutral position. As depicted in FIGS. 1 and 2, two right angle gearmotors 30 are typically used in a wheelchair 20, one to drive each drive wheel 24. The drive wheels 24 can therefore rotate independently of one another as called for by the controller (not shown). This is to enable the wheelchair 20 to make a tight radius turn, which is necessary in the confined spaces a wheelchair must operate in.
As shown in FIGS. 1 and 2, the gearmotors 30 on a conventional wheel chair 20 are quite large in size, taking up quite a large area of space on the wheelchair frame 22. The large area occupied by the conventional gearmotors 30 is to the detriment of the runtime of the wheelchair 20, as the space occupied by the gearmotors 30 limits the size of the batteries 26 that can be accommodated on the wheelchair frame 22. As another consequence of using the conventional right angle gearmotors 30, the large size of the gearmotors 30 translates to a heavier weight further reducing the runtime of the batteries 26. Typically, the batteries 26 can be recharged from a wall outlet, and any increase in weight of the wheelchair 30 comes at an expense of a reduction in battery life and runtime.
As further depicted in FIGS. 1 and 2, the safety brake on a conventional wheelchair 20 is an external brake 36 mounted on the end of the motor 32 portion of the gearmotor 30. Mounting the brake 36 external to the gearmotor 30 further increases the length of the gearmotor 30 and takes up additional space on the frame 22 that could better be used for the batteries 26.
Thus, although the right-angled gearbox and motor with external brake are commonly used as drive mechanisms on wheelchairs, they suffer several disadvantages. Power consumption is high. A large amount of space is required to accommodate a right-angled gearbox. The right-angled gearbox and motor are fairly large, thereby adding a significant amount of weight that will consume power and reduce the efficiency of the drive mechanism.
What is needed is a drive mechanism for an electrically powered vehicle that requires less space, is of lower weight, and improves efficiency over conventional drive mechanisms.